Laminated automotive interior trim panels are constructed in a variety of ways including the separate molding of a glass fiber reinforced polyurethane substrate and an expanded vinyl skin with a layer of polyurethane foam later formed in place between the substrate and skin to complete the panel. And the panel may be attached to the interior of a motor vehicle in various ways including the use of a common type of molded plastic fastener that (1) is adapted to be readily and quickly inserted and then retained in a cage attached to the substrate, and (2) is adapted to then readily and quickly attach the panel to the sheet metal of the vehicle structure which may be the body or a door and by a pushing force on the outer side of the panel that forces the fastener into a self-retaining condition in an aperture in the sheet metal. The fastener cage is typically a molded plastic part or assembly and it is desirable that the cage also be adapted for easy and quick installation on the substrate and prior to the formation of the foam so as to permit the cage to be anchored to the substrate from the back side. However, the foam which is formed in place against the back side of the substrate can not be allowed to enter the cage as it would block later entry of the fastener. This presents a problem because the internal fastener capturing feature(s) of the cage normally require that there be a central opening through the cage to permit the molding of the cage interior. As a result, such fastener cages are normally designed with a special molded plastic cap that is attached to the cage on the back side of the substrate to prevent such foam entry as disclosed in U.S. Pat. No. 4,717,301.
As mentioned above, the panel is attached by pushing on the panel to force the above type fastener into an aperture in the vehicle body or door structure. The panel is also required to be able to be pulled to force the release of the fastener from the vehicle structure for service or replacement of the panel. In raising the standards of its products, a motor vehicle manufacturer may require that the panel be capable of many repeated installations and removals such as five or more that would not normally be experienced in actual use and this places an unusual amount of repeated pushing and pulling stress on the connection of the fastener cage with the panel. In designing the cage for quick and easy installation on the substrate and with a foam blocker such as a cap, it has been found that current fastener cages are typically better suited for transmitting forces between the fastener and the substrate in one direction as compared to the opposite direction and as a result, the cage can be torn away or separated from the substrate on many repeated test installations and removals where repeated stress is placed on the weakest link between the cage and the substrate. For example, the fastener cage in the above noted U.S. Pat. No. 4,717,301 is substantially more secure in its connection with the panel to pulling rather than pushing on the panel to secure and release the fastener with respect to the structure to which the panel is attached by the fastener. And as a result, the cage is likely to be eventually torn from the panel on repeated installations.